Warning: Major spoilers ahead

Marissa Irvine arrives at 1800 Crescent Hollow Road to pick up her son, Milo, from a playdate. An older woman opens the door but says she’s got no idea what she’s talking about, causing her to apologise for the mistake. But her embarrassment for knocking on the wrong door turns to confusion, when she checks the text message she received from the mother she arranged with, Jenny, and realises she did have the right address.

Marissa explains to the woman that Milo was meant to be playing with Jenny’s son, Jacob, and that Jenny had told her they may be left with the nanny. The woman apologises, but says she’s there alone, with no knowledge of Milo, Jenny or Jacob. When she calls Jenny to see what’s going on, the phone number has been discontinued.

The woman lets her in so she can sort it out, with Marissa’s confusion quickly turning into panic. She notes she’d never been to the house before as it was Milo’s first play date as he is only five years old, but she’d met Jenny at the school social so trusted she was who she said she was. Marissa tries to rationalise what’s going on, thinking it was maybe an autocorrect issue in the text, so calls her own nanny, Ana, who also doesn’t pick up.

The woman suggests she call other parents from the class and gets through to Sarah, who’s at the park with her kids, and is confused by Marissa’s question, asking if she’d got her dates mixed up – Jacob is with her. She sends over Jenny’s number, but when she answers she’s in town on business, with no knowledge of a play date with Milo. Panicked, Marissa wants answers, but Jenny insists she never arranged for Milo to come over, and definitely never sent her a text. So, who did send her the message?

Marissa’s panic only heightens when she realises that a tracker she has in her son’s backpack has been taken offline. She knows the school would have called if he was never picked up, so someone must have got him. She calls her husband, Peter, who goes straight to answerphone, but when he calls back he knows nothing either.

It dawns on her she has no idea where her son is and he may have been taken.

Marissa drives back to her sprawling estate and frantically scrambles out of the car to see if somehow, someone has dropped him off. Running into every room, she wants to check if he’s maybe playing hide and seek, and even checks with Brian, Peter’s disabled brother who lives on the property, but it’s no use – he’s definitely not there. Her husband returns home and she drops into his arms in tears, hysterical.

The police are called, who question her on when she last saw him. She says she last saw him in the drop-off area outside of the school, but didn’t actively see him go in. Personal numbers for teachers aren’t given out, but his teacher is Mr Williams. They ask for distinguishing features, and they note his long blonde hair, and that he was wearing an orange shirt, blue trousers, and a green jacket with a dinosaur on it.

Questions quickly turn to the nanny, Ana, especially as she’s not answering her phone. Marissa explains they found her through a website that all the other school mother’s use, and she is vetted by the website, including criminal background checks. Marissa says Ana is Chilean, great with Milo, and trusts her completely, noting she lives away from the house and was away for the weekend with her boyfriend for a family wedding.

During the chat, she gets a call from a man called Darren, but chooses to ignore it, saying it was just work. She shares that she agreed to the playdate exclusively via text, saying Jenny reached out to her at a time when she needed to take a meeting, so it worked out. However, while talking with the cops she realises she barely knows Jenny, doesn’t know what she does for work, and had only spoken with her a week before the disappearance.

The number on the parent’s list also didn’t match the number she was messaging with, and she never spoke with her on the phone. Her husband reassures her it’s OK as her guilt sets in, saying she hadn’t got around to saving all the numbers on the list on her phone, so took the message “from Jenny” at its word because why wouldn’t it be right?

The police request a picture of their son.

Over in central Boston, Jenny calls her husband to share Marissa’s bizarre call, expressing concern for her. She then gets annoyed that her husband hasn’t left his job at the school yet, as he was supposed to be picking up Jacob from Sarah Larson’s.

She calls Sarah, who is bathing her youngest son, to apologise for running late, and Sarah tries to strongarm her into volunteering at a fundraiser, but she swerves it, moving the conversation onto what’s going on with Marissa. Sarah notes that it’s strange that Milo would go missing the same day their nanny goes out of town, saying it’s “shady”, and questions why they would pretend to be Jenny.

Young Milo is seen playing with his school friends, including Jacob, as Jenny arrives at the school orientation, led by Sarah. Handed an induction pack, complete with a school calendar of events and other essential info, she’s distracted by a text from her work, asking when she’s back in the office.

As Sarah makes her presentation, Marissa interjects with questions and quips that make Jenny and some of the other parents laugh. Meanwhile, Ana makes friends with someone who helps her fill out an information form, which the school needs for the kids’ safety. The woman asks “which one was hers” and she points out Milo, calling him “perfect”.

Back in the present day, Marissa continues to talk with police, who ask more questions about Ana, and whether Marissa’s parents live nearby. Peter begins to show how panicked he is too, insisting the police do everything they can. Marissa’s business partner, Colin, arrives at the door and tries to reassure her, but she’s distracted as she’s bombarded with calls from a big account. He offers to take it over for her so she can focus on Milo.

She tries calling Ana again and spots her phone going off on a couch outside in their garden – so they have no means of contacting her.

In Boston, Jenny joins work associates for a meeting and drinks, giving a proposal for an author to join her publishing imprint. She does well, but gets distracted by texts from her husband, and she later shares about the missing Milo. As husband Richie continues to hound him with questions, she eventually excuses herself.

As night draws in, Marissa and Peter hear a car pulling up in their driveway - it’s Ana. The pair run outside demanding to know where Milo is, but she has no idea what they’re talking about. Her car is empty, and she was only coming to the house to pick up her phone.

Detectives then share they’ve had a breakthrough, and that Milo was picked up by a woman named Carrie Finch. While Marissa and Peter have no idea who that is, it’s revealed to be the woman that helped Ana fill out her forms – who said she worked for Jenny.

Jenny arrives back home and rushes into the house, where police are interviewing Richie. Worried something is wrong with Jacob, she’s relieved to find him in bed undisturbed. The police ask them both questions about Carrie, including if she was ever violent. Jenny notes a time she thought Carrie was going to hit Jacob but says it was a misunderstanding as she was swatting at a fly. Jenny is informed that Carrie appears to have taken Milo and used a burner phone.

At the Irvines’ house, Brian and Peter’s sister, Lia, arrives, demanding to see the detective. Brian and Colin note she gave them both different stories about why she was so late getting there. Lia’s arrival makes Peter emotional, and she tries to cheer him up but he breaks down in tears.

Lia reassures him that they will find him before asking questions, immediately wanting to talk to Jenny and ask her questions. Peter tells her to let the police do their thing, but Colin backs her up, saying Jenny is a lead and could be responsible for not doing her due diligence.

In the city, the school parents of Bishop’s Academy attend a swanky dinner to socialise and get to know one another. Jenny is talking to Sarah and her husband, clearly bored as Sarah starts pushing her to get involved as volunteers, as “unofficially parents with only one child help the most, so it’s fair”.

She takes a breather in the bathroom, where she meets Marissa, who jokes about them wearing the same dress. The pair share a laugh together about it, before getting talking, with Marissa noticing Jenny isn’t doing OK. They both confess they’re only in the bathroom to escape the crowd, and Marissa sneaks out to grab them both wine. They spend the evening talking and laughing together in the restroom, describing how exhausted they are with having to be the “do it all” mothers.

As Marissa offers to help her get out of the fundraiser, the pair decide to grab a selfie, and Jenny notices a scar on her new friend’s shoulder.

Back in the present day, Jenny and Colin watch as the police search Carrie’s room, noting how surreal the whole situation is. Jenny expresses her guilt, but Colin says if she is the kidnapper, she would’ve found a way to do it. Jenny asks if she should go talk to the Irvines, but Colin says it would make them look guilty, telling her under no circumstances to apologise for anything.

Detectives Alcaras and Grecco arrive at the Irvines’ house, informing them that they’re treating this as a kidnapping, as it’s now been five hours and Milo’s tracker was found in the school’s parking lot, having been destroyed. While there’s been no communication about a ransom, it’s assumed whoever took him may want one, seeing as both Marissa and Peter work in finance, and they may reach out in the next 24 hours.

They ask if they’ve had any strange communication since he’s gone missing, which they haven’t, and Ana lies, saying she’s never spoken to Carrie before. The family are shown a picture to see if they recognise her, but they all say they haven’t. Marissa starts worrying about what happens if a ransom never comes, thinking it could be a paedophile or a trafficker that has taken him, causing Peter to break down again.

Marissa tries to comfort him, but instead he lashes out at her for not checking the number properly before accepting the play date. He immediately realises what he’s done and apologises, but Marissa is stunned and angrily walks off.

Jenny arrives at the house, walking up to the door just as Marissa storms out. She doesn’t know what to say apart from apologising, and the pair hold each other, both in tears. Marissa then brings Jenny into the house, introducing her to the group as her friend.

At the police station, Detectives Alcaras and Grecco look at the suspect board, with Grecco noting that “she has brought a lawyer with her” and bets she’d talk, as “she knows that we know Milo’s kidnapping was an inside job”. Alcaras notes that he “didn’t see it coming… these nice people, killing each other.”

Among the suspects on the wall are Marissa, Peter, Lia, Brian, Carrie, Colin, Jenny and Ana.